This patent document relates to nanostructures.
Certain useful properties of single-walled carbon nanotubes (SWNTs) have earned them numerous applications in different technological areas. Carbon nanotube field-effect transistors (CNTFETs) have acquired great importance due to their capability to switch on and off much faster than current silicon technologies and the foreseen limits in the downscaling of silicon transistor. In spite of significant progress made toward integrated nanotube circuits, the assembly and integration of nanotube electronics still faces significant challenges due to the coexistence of metallic and semiconducting nanotubes in as-synthesized samples.
Different approaches can be used to obtain CNTFETs containing only semiconducting nanotubes in the channels either by selective synthesis, post-synthesis separation methods, or post-synthesis methods to selectively etch metallic nanotubes. An alternative approach is to induce a metal-to-semiconductor transition in carbon nanotubes. Electron beam irradiation and hydrogen plasma have yielded metal-to-semiconductor conversion of SWNTs, but the limited size of the electron beam and instability of the plasma represent limiting hurdles for scalability.